1. Field of the Invention
The present invention relates generally to electromagnetic guns, and more specifically to electromagnetic gun and pulse forming network systems.
2. Discussion of the Related Art
Electromagnetic (EM) guns operate by storing a large amount of energy in one or more storage units over several seconds or minutes. This energy is then released over a period of hundreds of microseconds to milliseconds to the gun through a pulse forming network (PFN). The PFN controls an energy pulse or pulses so that the maximum energy is imparted to the projectile.
There are several types of EM guns. A rail gun is one of these. It is operated by placing a projectile between two electrically charged rails and creating an arc behind the projectile. The electromagnetic force created when the current flows up to the projectile, across to the adjacent rail and back down the adjacent rail causes the arc to move up the barrel and push the projectile ahead of it.
A second EM gun is a coil gun. With a coil gun, a series of coils surround the barrel, and the coils are energized in sequence starting from the back of the gun. As each coil is energized, the projectile is pulled into the coil like a solenoid.
A third type of gun which might use this invention is the Electrothermo Chemical (ETC) gun. While an ETC gun is not generally considered an EM gun, it does require a substantial discharge of energy to bring the chemical propellant up to temperature. Typically most of the energy for this type of gun is obtained from the chemical propellant and the amount of energy required from the PFN is significantly less than an EM gun.
There are a number of different methods of storing energy for an EM or ETC gun. Most of today""s large EM gun experiments are driven by electrostatic capacitor bank based energy storage devices. The capacitors are charged over a few seconds and then discharged through a PFN. Capacitor banks are normally modular in nature where several elements are connected in parallel or in series and parallel.
Rotating machinery such as a compulsator (compensated pulsed alternators) or homopolar generators is another method used to store energy for an EM or ETC gun. With this system, a rotating mass is spun at a very high speed and kinetic energy is stored in the speed of the rotating mass. To get the energy out of the rotating mass, it is slowed down using an electrical breaking method that results in a large current pulse emanating from the device. This current pulse is then shaped using a PFN and delivered to the gun barrel.
Electrolytic capacitors, as opposed to electrostatic capacitors can also be used to drive electric guns. The electrolytic capacitor generally has a longer time constant and sometimes has difficulty in responding fast enough to drive fast rail guns.
Two other devices that can be used for electric gun energy storage are batteries and chemical-double-layer capacitors. Like the electrolytic capacitor, both of these devices have a high energy density and relatively high internal impedance. The high internal impedance results in a relatively slow response time and high internal losses. For this reason, these devices are normally not used for large EM or ETC guns.
Modern EM Naval guns are being designed with ranges of 350 miles. To achieve this range, a 20 kg projectile requires a muzzle velocity of 2.5 kilometers per second km/s or a muzzle energy of 63 Mega Joules (MJ). To accomplish this, approximately 150 MJ needs to be delivered to the gun. The stored energy for such a system is approximately 200 MJ. Thus, regardless of the energy storage means, a substantial volume is required to store the energy that needs to be delivered to the gun.
In one aspect, the invention can be characterized as an electromagnetic gun system comprising a gun barrel coupled to a gun mount. The gun mount is coupled to a rotating deck and a pulse forming network is electrically coupled to the gun barrel. The pulse forming network is configured to rotate about an axis.
In another aspect, the invention can be characterized as a method for using an electromagnetic gun in a shipboard environment including the steps of obtaining an electromagnetic gun; obtaining a pulse forming network that comprises a substantially circular shape; coupling the electromagnetic gun to a rotatable deck on a surface of a ship; placing the pulse forming network in a substantially circular-shaped bulkhead located below the rotatable deck; providing energy from the ship to the pulse forming network; and providing pulsed energy from the pulse forming network to the electromagnetic gun.
In yet another aspect, the invention can be characterized as a capacitor module for a pulse forming network. The capacitor module comprises a capacitor disposed in a radial direction, and the capacitor includes an outer edge, an inner edge and side portions. The side portions couple the outer edge to the inner edge, and the outer edge and inner edge are substantially normal to the radial direction. The outer edge is thicker than the inner edge and the capacitor tapers from the outer edge to the inner edge such that a distance between the side portions is greater at the outer edge than at the inner edge.